The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Referring now to FIG. 1, a functional block diagram of an engine system 100 for a vehicle is presented. The engine system 100 includes an engine 102 that produces drive torque. Air is drawn into the engine 102 through an intake manifold 104. A throttle valve 106 varies the volume of air drawn into the intake manifold 104. The throttle valve 106 is actuated by an electronic throttle controller (ETC) 108, thereby controlling opening of the throttle valve 106. The air mixes with fuel from a fuel injector 110 to form an air and fuel mixture.
The air/fuel mixture is combusted within one or more cylinders of the engine 102, such as cylinder 112. In various engine systems, such as the engine system 100, combustion of the air/fuel mixture is initiated by spark provided by a spark plug 114. Exhaust gas resulting from combustion is expelled from the cylinders to an exhaust system 116. The exhaust system 116 includes an oxygen (O2) sensor 118 that outputs the concentration of oxygen in exhaust gas passing the oxygen sensor 118.
A driver instructs the engine 102 to start, and an engine control module (ECM) 130 then activates a starter (not shown) to start the engine 102. For example, the driver may turn a key and/or push a button to instruct the engine 102 to start. A driver input module 132 relays the driver's instruction to start the engine 102 to the ECM 130.
After the engine 102 is started, the ECM 130 regulates airflow into the engine 102 via the throttle valve 106 and the amount of fuel injected via the fuel injector 110. In this manner, the ECM 130 regulates the air/fuel mixture. The ECM 130 may regulate the air/fuel mixture to maintain a stoichiometric air/fuel mixture. The ECM 130 may also adjust the air/fuel mixture based on the output of the oxygen sensor 118.
After the engine 102 is started, however, the output of the oxygen sensor 118 may be unreliable until the temperature of the oxygen sensor 118 reaches a temperature threshold. When the output of the oxygen sensor 118 is unreliable, the ECM 130 may regulate the air/fuel mixture in an open-loop mode. In the open-loop mode, the ECM 130 regulates the air/fuel mixture without considering the output of the oxygen sensor 118.
The ECM 130 may estimate that the output of the oxygen sensor 118 will be reliable, for example, when a timer expires after the output of the oxygen sensor 118 leaves a calibratable voltage window. For example only, the ECM 130 may estimate that the output of the oxygen sensor 118 will be reliable twenty (20) seconds after the output leaves a voltage window between 200 mV and 600 mV. In such implementations, the ECM 130 may estimate that the output of the oxygen sensor 118 will be reliable approximately thirty-five (35) seconds after the engine 102 is started.